The purpose of this research is to gain a better understanding of various factors that affect the use of needed physician services within a community and to examine the relations among them. A systems approach is used to integrate attributes of the population (age, income, etc.), health care resources (manpower, facilities, etc.), barriers to care (distance, insurance coverage, etc.) and the use of needed services. Data from the Household Health Surveys, conducted by the Experimental Health Services Delivery Systems, are linked with data from the American Medical Association, the American Hospital Association and the Bureau of the Census. Variables are classified as amenable or not amenable to policy intervention. Health care resources receive special attention in the analysis because of their importance to health planners under the provision of the Health Planning and Resources Development Act (P.L. 93-641). The study is designed to assist planners by demonstrating the use of survey and extant data, aggregate and disaggregate levels of analysis, and the systems approach applied to small areas. The research extends ongoing efforts by increasing the number of sites in which the model is tested, adding further information about health care resources, developing alternative measures of needed services, employing synthetic estimates as proxies for those derived from local survey data, and examining the use of services by those who do not need them.